Insurgents may threaten Iraq's dams as much as its oil -- with potentially dire consequences.

The turmoil in Iraq already has the world worried about the safety of the country’s mammoth oil fields. Now Iraqis must imagine massive waves of water crashing downriver from the country’s shaky dams, which are smack in the terrorists’ crosshairs.

On Monday, Islamist insurgents in the Islamic State, formerly known as the Islamic State of Iraq and al-Sham, renewed their offensive in Iraq’s Anbar province, moving toward the key hydroelectric dam of Haditha. The dam’s security has concerned U.S. officials for years and protecting the country’s second-biggest dam was a priority objective during the 2003 invasion.

Meanwhile, Iraq’s biggest dam, the Mosul dam, is right next to a hotbed of Islamic State activity and poses catastrophic risk even if the terrorists don’t open the floodgates or blow it up. If the dam fails, scientists say Mosul could be completely flooded within hours and a 15-foot wall of water could crash into Baghdad.

ISIS fighters first moved toward the Haditha Dam, located in western Iraq on the Euphrates River, last week. On Monday, the insurgents and other tribal Sunni troops resumed the advance, according to the Institute for the Study of War.

On Wednesday, Sunni connivance around Haditha increased, with reports that disparate militant groups and tribal leaders were negotiating the surrender of the town of Haditha, which would open the whole of Anbar province to ISIS.

The latest advances come as the beleaguered Iraqi government, led by a recalcitrant Shiite, continues to refuse to discuss political reconciliation among Iraq’s Sunni, Shia, and Kurdish sects, which have found themselves increasingly at loggerheads with each other.

The Obama administration and its allies have been pressing Iraqi Prime Minister Nouri al-Maliki to either make a serious effort to reconcile with the country’s embittered Sunni and Kurdish minorities or step aside so a new leader could take the fight to ISIS. In remarks Wednesday, however, the embattled Iraqi prime minister dismissed those demands and said fighting ISIS on the battlefield was more important than striking the political deals necessary to keep his country’s warring factions from pulling further apart.

"The battle today is the security battle for the unity of Iraq," he said on state television. "I don’t believe there is anything more important than mobilizing people to support the security situation. Other things are important, but this is the priority."

Maliki’s remarks came as insurgents kept Iraqi soldiers from reclaiming Tikrit, the birthplace of former Iraqi leader Saddam Hussein; the United Nations released new figures showing at least 2,400 Iraqis died last month, making it one of the bloodiest periods since the 2003 U.S. invasion.

Iraq’s government has tried to push back against the rebels with increased airpower, including the first installment of fighter jets from Russia–and, by some accounts, from Iran. U.S. air assets, especially armed drones, have also been thrown into the fight against the Islamist insurgents.

Iraq’s hydroelectric facilities represent a soft underbelly in the fight against ISIS. A compromised Haditha Dam would be a serious threat to western and southern Iraq: It provides power for the capital and controls water supplies for irrigation downstream. Using Haditha, ISIS could flood farmland and disrupt drinking water supplies like it did with a smaller dam near Fallujah this spring. By threatening Karbala and Najaf, holy cities for Shiites, the Sunni insurgents hoped to pressure the Shiite-led government in Baghdad. (On Tuesday, ISIS apparently attacked an iconic Shiite mosque north of Baghdad; when al Qaeda attacked that mosque in 2006, it sparked massive sectarian violence.)

The Haditha Dam is a crucial chunk of Iraqi infrastructure. And its massive reservoir–Lake Qadisiyah–is a potential weapon of mass destruction. During the 2003 invasion of Iraq, a small unit of U.S. Army Rangers seized Haditha Dam to prevent Saddam Hussein’s forces from destroying it and causing a massive flood. In 2005, insurgents twice attacked Haditha with explosive devices but did not major damage.

As U.S. troops withdrew from Iraq, Haditha’s security became more troublesome. A 2009 assessment by the Special Inspector General for Iraq Reconstruction, or SIGIR, found that a $1 million U.S.-funded effort to boost Iraqi government security at the site was inadequate; a chain-link perimeter fence, for example, was poorly built and sections were already falling down when Americans inspected the site.

"Destruction of the dam would greatly affect the functioning of the country’s electrical grid and would cause major flooding downstream," the report warned.

Dams are vulnerable in other countries, too. For decades, the United States has tried to help Afghanistan complete the Kajaki Dam in the troubled Helmand province in the southern part of the country. The partially finished dam has become a source of intermittent electricity for the impoverished region–but also a source of revenues for Taliban officials who have at different times been a de-facto government in the area.

Kajaki, too, has a history as a potential tool of terrorists. Before the 2001 U.S. invasion of Afghanistan, Taliban officials toyed with the dam’s water flow to put pressure on Iran, which is downstream. In 2007, NATO troops repelled a Taliban attack on the dam. After the final U.S. withdrawal from Afghanistan, Kajaki and its massive reservoir could represent another potential weapon in the hands of insurgents.

In Iraq, if the Haditha headache weren’t enough, a compromised Mosul Dam is a migraine. It lies just north of a new ISIS stronghold. What’s worse, it could unleash a torrent of destruction even without sabotage.

Built in the late 1980s, it has owned the title of "most dangerous dam in the world" for years, according to a 2006 assessment by the U.S. Army Corps of Engineers. It was built on an unstable foundation of water-soluble rock in an area prone to sinkholes. As a result, it is injected with grout around-the-clock to maintain structural integrity. Gen. David Petraeus, the former U.S. commander in Iraq, urged Iraqi Prime Minister Nouri al-Maliki to prioritize bolstering the dam in 2007. A U.S.-funded, $27 million plan to address the most glaring problems was found wanting by SIGIRthat same year.

Although apparently unmolested by ISIS so far, a worst-case scenario could unfold even if it becomes just collateral damage.

If the ISIS offensive disrupts the dam’s intensive maintenance, it could further deteriorate or even be breached. Researchers say it could send as much as 50 million gallons of water per second crashing toward Mosul that would cover more than half the city under 25 meters of water within hours. Further down the Tigris River, Baghdad itself could be under 4 meters of water within three days. It would also wipe out more than 250 square kilometers of prime farmland.

"The only measure which can reasonably be taken to reduce the risk to downstream populations" is building another dam downstream, researchers concluded earlier this year. Construction started on the Badush Dam in the 1990s but never completed.

Mosul Dam’s regular maintenance appears to continue uninterrupted by ISIS, said researchers at Lulea University of Technology in Sweden, who have studied the dam. The dam’s manager declined to discuss the facility’s state or the risks posed by ISIS.